DAR-309

Added pl translations
Corrected documentation for i18n
DAR-309

Code review changes:
- newlines at EOF
- removed abstraction unnecessary at this point
- removed accidental newline added to MustacheService
DAR-309

Added caching
DAR-309

Small copy tweaks
DAR-309, removing empty lines at the end of templates
DAR-309, applying mediawiki code standards
DAR-309, fixing TODO comment
DAR-309, adding missing translation
DAR-309, adding new lines at the end of file - mediawiki code standards
DAR-309, adding new line separatation between css rules
DAR-309, use wgAutoloadClasses directly
DAR-309, fix sass import paths
DAR-309, change hardcoded corporate wiki link to i18n mesage
Merge pull request #956 from Wikia/DAR-309

DAR-309
placeholders for ui components, README.md
moved ui_components directory
added two more messages
removed F::app()
added UIFactory class, used it in SpecialStyleguideDataModel, changed SpecialStyleguideDataModel::getSectionData() method
nasty hacks to make GlobalHeader hack working correctly